'Sherlock' faces the hardest case of his career in twisty Season 4 premiere

This recap contains spoilers for Sherlock Season 4, episode 1, titled "The Six Thatchers."

Any true fan of Sherlock Holmes — in any of his myriad incarnations — knows that there's no competing with the bromance between Holmes and Watson; it's right up there with Kirk and Spock in the pop culture pantheon of epic friendships.

Which means that any character who comes along to distract one of our heroes from their noble mission of crime-fighting and witty-bantering is inevitably doomed to become a mere footnote in their sweeping saga (no matter how sharp and self-sufficient they may be).

This was true of Mary Watson (née Morstan) in Sir Arthur Conan Doyle's stories, and after the devastating Season 4 premiere, it's also true of Sherlock — although creators Steven Moffat and Mark Gatiss inarguably gave the character more depth and chutzpah than Doyle ever did before deciding to kill her off.

Indeed, Mary's demise was such an afterthought in his novels, Doyle never even gave a cause for it — a far less poetic end than Mary's decision to sacrifice herself by jumping in front of a bullet to save Sherlock's life, having previously tried to shoot him herself.

Dramatic irony aside, it seems questionable that a new mother would take a bullet for a man she grudgingly admired but clearly also resented, no matter how many previous sins she felt the need to atone for.

From a storytelling standpoint, there's no better catalyst for shattering Sherlock and John's relationship, but it still felt like the writers were taking the easy way out by dispatching Mary so neatly.

At a press screening, Moffat admitted that the decision to kill Mary off so early (she was only introduced at the beginning of Season 3, lest we forget) was a way to keep Holmes fans on their toes.

"Mary's been dead for 100 years, so it's hard to surprise people in those circumstances," Moffat said, according to Digital Spy. "The only thing we could do was do it earlier than people expected, so that it would happen as wrenchingly and as horrifically as such things happen in real life. So that's what we went for — and obviously while Mary and Sherlock were very close, there was that moment of froideur when she shot him! So it was nice to reverse that and have her save his life."

It seems typically Moffatian that we finally learned more about Mary's intriguing backstory just before we lost her, but the mystery surrounding her work with AGRA proved to be a compelling framework for the episode.

The deep dive into Mary's past was made all the more gripping thanks to Rachel Talalay's taut direction — which not only gave us some of the show's most cinematic action scenes to date, but also supplied endless rope for us to skip with in the playful first half, before it inexorably began to tighten towards the episode's painful conclusion.

Benedict Cumberbatch and Martin Freeman

Image: PBS

Now John is a devastated single father, isolated from his two major support structures — his wife and his best friend — and dealing with the unresolvable guilt of having indulged in an emotional (hopefully, that's all it was) affair that he can now never seek absolution for.

As Mary points out to Sherlock in a heartbreaking video message delivered after she's dead, she has just given the detective the hardest case of his career — a mission to save John Watson when he doesn't want to be saved.

Having goaded Mrs. Norbury into taking a shot at him with a typically smug display of showboating rather than simply taking the win and shutting up, Sherlock rightly feels responsible for Mary's death (now we know why the Season 3 finale was titled "His Last Vow," — he's obviously learned his lesson) but at least it's clear that he's taking his failure seriously. The final minutes of the episode see him in a position we never would've expected to find him: in a therapist's office.

Only his love for John could force Sherlock into such an uncomfortable situation, and it's reassuring to see that the stubborn sleuth is actually capable of some growth and introspection after all this time.

That full circle theme pervades the premiere. The rollocking opening act sees Sherlock at the top of his game, practically solving cases in his sleep, which makes the juxtaposition of his uncertainty and guilt in the closing minutes all the more potent. This is Sherlock as we've never witnessed him, and that's a delicious prospect, even for fans who delight in watching him snark and sneer his way through every mystery he's faced with.

Holmes and Watson may be broken, for now, but the game is still on — the question of Moriarty's inexplicable reappearance (at least in digital form) lingers, as does the subtle promise of the fabled third Holmes brother — after Mycroft puts in a mysterious call to "Sherrinford" near the end of the episode.

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